The concept of free flight introduces many challenges for both air and ground aviation operations. Of considerable concern has been the issue of moving from centralized control and responsibility to decentralized control and distributed responsibility for aircraft separation. Data from capacity studies suggest that we will reach our capacity limits with ATC centralized control within the next 2 decades, if not sooner. Based on these predictions, research on distributed air-ground concepts was under taken by NASA Advanced Air Transportation Technologies Program to identify and develop air-ground concepts in support of free-flight operations. This paper will present the results of a full mission air-ground simulation conducted in the NASA Crew Vehicle Systems Research Facility. The purpose of the study was to evaluate the effect of advanced displays with “intent” (4-D flight plans) information on flight crew and ATC performance during limited free-flight operations. To assess the value of 4/D intent information (flight plans) flight crews performed real time, strategic, flight path re-planning with and without flight plan information on surround traffic during en route free flight operations. To support the re-planning task flight crews used an enhanced cockpit situation display (CSD) and a route assessment tool to identify traffic conflicts and develop alternative de-conflicted flight plans. The modified de-conflicted flight plan was then submitted to ATC for approval, and after approval loaded into the autopilot (FMS). Two levels of ATC authority were evaluated during the study: (1) limited authority - ATC would only intervene if a loss of separation were imminent; (2) full authority - ATC would run the sector as they would normally. After loading the new flight plan it was data linked to all surrounding traffic. The results of the study suggest that flight crews with advanced 4-D flight plan information can perform strategic self-separation during operations in densely populated traffic environments. And when ATC remains in the information and approval loop, flight deck strategic self-separation is not disruptive to normal ATC sector operations. The results also showed that when flight crews had access to 4-D flight plan information they were more efficient and their workload was reduced; they made smaller deviations for traffic, reduced their trip length for non-traffic related maneuvers, and had fewer ARAT (advanced route assessment tool) events. Crew responses to 3-D and 4-D traffic information, display de-clutter features, and the advanced flight re-planning tools were positive overall, however they rated both dial and touch-pad input controls neutral.